摘要:

Bean plants grown under various controlled moisture conditions in a greenhouse, and sprayed with 2,4-D, showed differences in catalase activity, carbon dioxide output, total nitrogen content, and visual response. Catalase and respiration of leaves were stimulated or depressed depending upon soil moisture, concentration of 2,4-D, and time after treatment, but there was not always a positive correlation between the two activities. Protein in leaves, with a few noteworthy exceptions, was decreased by 2,4-D. Extremes among leaf responses were induced in plants recently deprived of optimum moisture. Catalase, respiration, and protein content of stems were greatly increased by 2,4-D. This was especially noticeable in plants in moist soil. Soil treatments with 2,4-D solution followed by adequate moisture effected, in above-ground parts of plants, responses resembling those measured after foliage sprays on beans in moist soil. Fasciation of underground parts resulted only from a soil application involving relatively dilute (50 p.p.m.) concentration of 2,4-D.

ISSN:1923-4287    

DOI:10.1139/cjr50c-023

出版商:NRC Research Press    

年代:1950

数据来源: NRC

摘要:

Sixty-two species, seven hybrids, eleven varieties, and two forms ofCarex, and one species ofKobresiaoccur on Anticosti, a 135-mile long island located in the mouth of the St. Lawrence River.After a few historical notes on the early surveys of the Anticosti flora, the author lists in their natural order the different species ofCarexoccurring on the island, consisting mainly of collections made by Macoun, Schmitt, Frère Marie-Victorin, and his field-associate F. Rolland-Germain, and Jacques Rousseau. Each species has its respective distribution and proper bibliography given. Two new hybrids are described.In the third part, the author gives some phytogeographical conclusions. The sedges enumerated fail in the following categories:1. Arctic-alpine species at their southernmost limit or nearly so:Kobresia simpliuscula,Carex microglochin, andC.rupestris.2. Euryatlantic species, i.e. species occurring on both sides of the Atlantic, but very often with their main area in Europe:C.Hostiana,C.demissa,C.Hartmani,C.flava.3. Species of the upper subarctic:C.capillaris,C.rariflora,C.media, etc.4. Species of the lower subarctic:C.exilis,C.atratiformis,C.pauciflora,C.sterilis,C.castanea,C.Buxbaumii, etc.5. Cold-temperate species at their northernmost limit:C.arctata,C.Crawfordii,C.Deweyana,C.eburnea,C.intumescensvar.Fernaldii,C.leptonervia,C.pedunculata,C.retrorsa,C.scoparia,C.tribuloides,C.viridula,C.vulpinoidea, etc.A line drawn from Anticosti island to Lake Mistassini and James Bay seems to constitute an important natural limit for many species in the flora of Quebec.6. Halophytic species:C.hormathodes,C.Lyngbyei,C.Mackenziei,C.nigra,C.paleacea,C.recta.C.Lyngbyei, a species of arctic shores, has its southernmost limit on Anticosti island.Special consideration is given to the members of the critical sectionEXTENSAE(theflava-group) and their numerous hybrids.The general conclusion is that Anticosti belongs to the colder part of the temperate zone, with arctic or subarctic "islands" on the river flats, on windswept cliffs, or in bogs.The author concludes with a few notes on the economical value of sedges as pasture and their relation to deer-grazing.

ISSN:1923-4287    

DOI:10.1139/cjr50c-024

出版商:NRC Research Press    

年代:1950

数据来源: NRC

摘要:

Intensive cultural studies withThielaviopsis basicola(Berk. & Br.) Ferraris, the cause of the black rootrot disease of tobacco, showed that it exists in nature in two distinct forms, which have been called brown and gray wild types, and which are differentiated by their cultural characteristics on potato dextrose agar. The brown wild type usually is the predominant form isolated, although in some instances the gray predominates in mixed infestations. It is suggested that the balance between the two types is determined, in part, by a differential selective action of the soil flora. The gray wild type is less pathogenic and is more poorly adapted than the brown to withstand long dormant periods. The latter occasionally mutates to the gray in soil, host, and in artificial culture. In a few instances, but only in association with host passage, the gray wild type has mutated to the brown. The wild types do not remain stable on media which support abundant saprophytic growth but give rise to and are crowded out or replaced by cultural mutants. The wild type can be maintained with a minimum of variation in soil, soil agar, roots, or similar substrates (low in certain nutrients). Variations in the morphology and behavior of endoconidia consisted of the production of endoconidial yeastlike colonies and the formation of thick-walled chlamydosporelike structures from thin-walled endoconidia. Some endoconidia are as resistant as chlamydospores to long periods of dormancy, heat, and drying. Fungus morphology in the host was characteristic for each of the three phases of cell penetration, cell colonization, and the production of chlamydospores and endoconidia. Root invasion byThielavia basicolawas common only in association withThielaviopsis basicolawhich suggests a commensalistic relationship between these two fungi.

ISSN:1923-4287    

DOI:10.1139/cjr50c-025

出版商:NRC Research Press    

年代:1950

数据来源: NRC